JPH0372537A - rubber composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a rubber that is made from a solution-polymerized styrene-butadiene copolymer rubber having a high proportion of trans-1,'44 bonds and a diene rubber other than the above. It relates to a composition, and more specifically, a styrene-butadiene copolymer rubber with a high amount of trans-1,4 bond gold obtained using a composite catalyst containing an alkaline earth metal, and a diene-based rubber with a relatively low glass transition temperature. This invention relates to a rubber composition that is free from rubber.

(Prior art) Diene rubber has traditionally been used as the main material for rubber materials for large tires used in trucks, buses, and even aircraft.In particular, natural rubber has been used to improve heat generation and fracture resistance.
In addition, it is common to use styrene-butadiene copolymer rubber to improve abrasion resistance and cut resistance, and polybutadiene rubber to further improve abrasion resistance. Rubber composites made by mixing appropriate amounts of rubber materials have been used.

As for the rubber of large tires, especially the tread part, natural rubber is mainly used because the load on the tire is extremely high, and it is common to blend it with polybutadiene rubber.

However, since abrasion resistance and crack resistance, which are important properties for large tires, are contradictory properties, in a mixture of natural rubber and polybutadiene, the wear resistance improves as the amount of polybutadiene rubber increases. , the crack resistance is poor, and in small amounts the crank resistance improves, but
Abrasion resistance will decrease.

For this reason, efforts have been made to improve polybutadiene rubber, and numerous reports have been made.
For example, a method using polybutadiene rubber with a wide molecular weight distribution to improve tack and green strength (Japanese Patent Application Laid-open No. 59
-45337), and when trying to improve abrasion resistance, methods include increasing the molecular weight of polybutadiene rubber in addition to using fillers such as carbon black, but in this case, the abrasion resistance Although it is improved, there is a problem that it causes a decrease in workability.

Furthermore, due to the recent improvement in road paving rates, the spread of expressways, the soaring price of gasoline, and the social trend toward energy conservation, the demand for large tires has become similar to that for passenger car tires. In addition to abrasion resistance and cut chipping resistance, transfer resistance has become a very important tire characteristic from an economic standpoint, and skid resistance and high-speed durability from a safety standpoint.

That is, social demands have led to demands for large tires that maintain skid characteristics and abrasion resistance at conventional levels and also have reduced transfer resistance. in general,
Lowering the transfer resistance also lowered the wet skid resistance, and these two properties were contradictory and in a trade-off relationship. By the way, it has been discovered that this antinomy relationship can be broken when a high-vinyl type solution polymerized styrene-butadiene copolymer rubber (hereinafter abbreviated as solution polymerized SBR) is used (U.S. Pat. No. 4,334,567). The use of high-vinyl solution polymerized SBR in fuel-efficient tires for automobiles is becoming common.

In addition, the applicant proposed that fuel efficiency could be further improved by modifying the terminal end of this SBH with a compound having a specific atomic group (Japanese Patent Publication No. 1-21178, Japanese Patent Application Laid-Open No. 61-42552) ).

(Problems to be Solved by the Invention) However, tires for large trucks and buses made using these high vinyl solution polymerized SBRs have extremely poor wear resistance, and cannot be put to practical use. Further, the strength characteristics of the SBH are not sufficient for use in large tires.

Regarding wear resistance, passenger car tires using the SBR are still not sufficient, and improvements are required.

An object of the present invention is to provide a rubber composition with improved strength properties and wear resistance that can be used to manufacture large tires.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned drawbacks, and have found that a solution-polymerized styrene-butadiene copolymer rubber containing an extremely high proportion of trans-1,4 bonds has extremely excellent properties, especially high green strength and fracture strength. It has been discovered that by mixing this rubber with an appropriate amount of diene rubber such as natural rubber, the balance between abrasion resistance and crack resistance can be improved without reducing the breaking strength.The present invention is based on the present invention. reached.

Furthermore, the present inventors have also discovered that the abrasion resistance and strength characteristics can be further improved by introducing a specific atomic group into the molecular chain of the copolymer rubber, leading to the present invention.

(Means for Solving the Problems) Thus, according to the present invention, the styrene content obtained by solution polymerization is less than 20% by weight, and the trans-
Styrene-butadiene copolymer rubber containing 90% by weight or more of 1,4 bonds (1) 10 to 40% by weight and diene rubber other than the above having a glass transition temperature of 160°C or less (2) 60 to 40% by weight
Provided is a rubber composition characterized in that it contains 90% by weight of the rubber component.

The styrene-butadiene copolymer rubber obtained by solution polymerization used in the present invention has a styrene content of 2.
less than 0% by weight, trans-1 of the butadiene moiety,
The amount of 4 bonds is 90% by weight or more. Styrene content is 2
If it exceeds 0% by weight, wear resistance will decrease. Preferably it is 5 to 15% by weight. Trans-1,4 bond amount is 90
If it is less than % by weight, wear resistance and fracture strength will decrease.

The copolymer rubber is usually polymerized using a composite catalyst containing an alkaline earth metal, but at present no one with a trans-1,4 bond content of more than 95% by weight has been obtained. % or more, the effects of the present invention should naturally be obtained.

The rubber composition of the present invention has a mixture of this styrene-butadiene copolymer rubber and a diene rubber having a glass transition temperature (Tg) of -60°C or lower as a rubber component.

The mixing ratio of the styrene-butadiene copolymer rubber is 10 to
If the content is less than 10% by weight, the abrasion resistance will not be improved, and if it exceeds 40% by weight, the abrasion resistance will be improved, but the fracture strength, cut resistance, and crank resistance will deteriorate. Preferably it is 15 to 30% by weight.

If the Tg of diene rubber exceeds 160°C, the durability will be particularly poor for large tires that are used under much harsher conditions than for general passenger cars, which is undesirable.The mixing ratio of diene rubber is 60 to 90% by weight. %. If it is less than 60% by weight, the breaking strength, cut resistance, and crack resistance will be poor;
If it exceeds 0% by weight, wear resistance will decrease. Preferably 7
It is 0 to 85% by weight.

Examples of the diene rubber include, but are not limited to, natural rubber, polybutadiene rubber, polyisoprene rubber, butadiene-styrene copolymer rubber, and butadiene-isoprene copolymer rubber.

The styrene-butadiene copolymer rubber having a high amount of trans-1,4 bonds of the present invention is usually obtained by copolymerizing butadiene and styrene using a composite catalyst containing an alkaline earth metal. Examples of composite catalysts containing alkaline earth metals include JP-A-51-115590 and JP-A-52-
9090.17591.30543.48910°98
077; JP-A-56-112916.118403.
Examples include, but are not limited to, catalyst systems containing compounds such as barium, strontium, and calcium as main components, which are disclosed in publications such as JP-A-57-100146.

In the present invention, the copolymer rubber having an active terminal after completion of polymerization and an N-substituted amino(thio)ketone, an N-substituted amino(thio)aldehyde, or a compound having the general formula 10-
By using a terminal-modified styrene-butadiene copolymer rubber obtained by reacting with a compound having an atomic group represented by Nζ (in the formula, M represents oxygen or sulfur 1 yellow atom), in addition to the above-mentioned advantages, Transfer resistance is also improved.

The organic compounds used in the terminal modification reaction are as follows:
4-dimethylaminobenzophenone, 4-diethylaminobenzophenone, 4-di-1-butylagonobenzophenone, 4-diphenylbenzophenone, 4.4'-bis(dimethylamino)benzophenone, 4.4'-bis(diethylamino)benzophenone, 4.4'-bis(
di-t-butylamino)benzophenone, 4.4'-bis(diphenylamino)benzophenone, 4.4'-bis(divinylamino)benzophenone, 4-dimethylaminoacetophenone, 4-diethylaragonoacetophenone, 1.3- 4-Dimethyl N-substituted atonaldehydes such as aminobenzaldehyde, 4-diphenylaminobenzaldehyde, 4-divinylaminobenzaldehyde and corresponding N-substituted aminothioaldehydes: N
-Methyl-β-propiolactam, N-t-butyl-β
-propiolactam, N-phenyl-β-propiolactam, N-methoxyphenyl-β-propiolactam,
N-naphthyl-β-propiolactam, N-methyl-2
-pyrrolidone, Nt-phthyl-2-pyrrolidone, N-
Phenyl-pyrrolidone, N-methoxyphenyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-benzyl-2-pyrrolidone, N-naphthyl-2-pyrrolidone, N
-Methyl-5-methyl-2-pyrrolidone, N-t-butyl-5-methyl-2-pyrrolidone, N-phenyl-5-
Methyl-2-pyrrolidone, N-methyl-3,3'-dimethyl-2-pyrrolidone, N-t-butyl-3,3'-dimethyl-2-pyrrolidone, N-phenyl-3,3'-dimethyl-2 -pyrrolidone, N-methyl-2-piperidone, N-t-butyl-2-pyrrolidone, N-phenyl-2
-piperidone, N-methoxyphenyl-2-piperidone, N-vinyl-2-piperidone, N-benzyl-2-piperidone, N-naphthyl-2-piperidone, N-methyl-3,3'-dimethyl-2-piperidone , N-phenyl-3,3'-dimethyl-2-piperidone, N-methyl-
ε-caprolactam, N-phenyl-ε-caprolactam, N-methoxyphenyl-ε-caprolactam, N-
Vinyl-ε-caprolactam, N-benzyl-ε-caprolactam, N-naphthyl-ε-caprolactam, N-
Methyl-ω-laurirolactam, N-phenyl-ω-laurirolactam, N-t-butyl-ω-laurirolactam, N-vinyl-ω-laurirolactam, N-benzyl-ω-laurirolactam, etc. N-substituted lactams and their corresponding thiolactams; 1,3-dimethylethyleneurea, 1,3-diphenylethyleneurea, 1,3-di-t-butylethyleneurea, 1,3-divinylethyleneurea, etc. N-? Examples include compounds having the general formula -C-anal dibond (X represents an O3S atom) 1 in the molecule, such as Z-substituted ethylene ureas and corresponding N-substituted thioethylene ureas. The amount of these compounds used is usually 0.05 to 1 per mole of the polymerization catalyst used.
0 mol, preferably in the range of 0.2 to 2 mol. The reaction usually proceeds in a range of room temperature to 100° C. in several seconds to several hours. After the reaction is completed, terminally modified styrene-butadiene copolymer rubber is recovered from the reaction solution by steam stripping.

In addition, in the present invention, as the copolymer rubber, 5nCj
! a+5iCj! Rubbers coupled with known coupling agents such as a may also be used.

The transfer resistance of the acid product of the present invention can be further improved by using a diene polymer rubber to which the above compound has been added as the diene polymer rubber to be blended with the high trans SBR.

The rubber composition of the present invention is produced by mixing the above-mentioned rubber components and various compounding agents using a mixer such as a roll or Banbury mixer.

The various compounding agents to be used can be selected from those commonly used in the rubber industry, and those suitable for the intended use of the rubber m-acid.
There are no particular restrictions.

Usually, vulcanization systems include sulfur, stearic acid, zinc white, various vulcanization accelerators (thiazole, thiuram, sulfenamide, etc.), or organic peroxides, and reinforcing agents include HAF, l5AF, etc. Various grades of carbon black, silica, etc., fillers include calcium carbonate, talc, etc., and other compounding agents include process oil,
Processing aids, vulcanization retarders, anti-aging agents, etc. are used. The types and amounts of these compounding agents are selected depending on the intended use of the rubber composition, and are not particularly limited in the present invention.

According to the present invention, a rubber composition can be obtained which has improved breaking strength, abrasion resistance, crack resistance, and a balance between transfer resistance and wet skid as compared to conventionally obtained rubber compositions. The rubber composition of the present invention is suitable for treads of passenger car tires and large tires.

(Example) The present invention will be described in more detail with reference to Examples below. Note that parts and percentages in Examples and Comparative Examples are based on weight unless otherwise specified.

The butadiene unit of the polymer used has a cyclostructure (cis-
1,4, trans-1,4 and 1,2-bonds) using an infrared spectrometer and the method of Morero et al.
Chis', e Ind, , , 41.758 (19
59) ), and the styrene content is 500MH2
' Determined from H-NMR measurement. Further, the extrapolated onset temperature of the DSC curve was defined as the glass transition temperature (Tg).

(Production Example) A method for preparing solution polymerized rubber used in the following examples will be described.

A stainless steel polymerization reactor with an internal volume of 151 kg was washed, dried, and replaced with dry nitrogen, and then 7000 g of cyclohexane was added.
, styrene and 1,3-butadiene in the amounts shown in Table 1. Thereafter, a dibutylmagnesium/triethylaluminum complex (molar ratio Mg/AN=5) (the amount of the complex is based on magnesium) and di-L-butoxybarium are added in the amounts listed in Table 1. 60℃ while stirring the contents
Polymerization was carried out for 5 hours.

After the polymerization reaction was completed, 0.05 mol of the reactants listed in Table 1 was added, and an addition reaction was carried out for 30 minutes. Then add methanol 1. Omj! Add 2 to the polymer solution to stop the addition reaction and take out the polymer solution from the polymerization reactor.
．． 6-di-t-butyl-p-cresol (BHT), 8
g, remove the solvent by steam stripping,
The polymer was solidified.

The coagulated polymer was dehydrated using a roll and dried under reduced pressure at 60°C for 24 hours.

The properties of the obtained polymer are shown in Table 1.

Example 1 The mixed rubbers shown in Table 3 were used as rubber components, and these mixed rubbers were mixed with various compounding agents having the formulations shown in Table 2, and the capacity was 250 mj! The mixture was kneaded and mixed in a Gravender type mixer to obtain each rubber compound m-acid. These rubber compound compositions were press-vulcanized at 150° C. for 30 minutes, test pieces were prepared, and the physical properties of the vulcanized products were measured. These results are shown in Table 3. Note that the Tg of natural rubber (NR) is -67°C.

The evaluation method is as follows. Breaking strength (tensile strength) was measured according to JIS K-6301. In addition, the rebound resilience was measured using a Dunlop trypsometer at a temperature of 60°C.
was measured and converted into an index of transfer resistance. Further, the abrasion resistance was measured using a Gudrich 2-Pico abrasion tester according to STM-D-2228, and converted into an index. Wet skid resistance was measured using a portable skid tester at 23°C using ASTM-I! It was measured on a road surface of 303-74 and converted into an index. Note that the conversion of each of the above properties was performed by setting each property of the vulcanized compound composition of Experiment No. 9 as 100. The results are shown in Table 3.

From the results in Tables 2 and 3, it is clear that the rubber composition of the present invention maintains a high level of tensile strength, has improved abrasion resistance, and has a good balance between wet skid resistance and transfer resistance (anti-rolling elasticity). It can be seen that the results have also improved.

(ml) Styrene and butadiene were copolymerized using an n-butyllithium polymerization catalyst (hereinafter abbreviated as 'Li-5BR).

Styrene content 17.2%, 1,2-bond content 11.
3%Tg -76°C1 Muni viscosity (ML+ +a
, 100°C) 33 Example 2 A rubber composition using a mixed rubber of Polymer C shown in Table 1 and a diene rubber shown in Table 4 whose Tg is below 160°C and above -60°C as raw rubber. The physical properties of the vulcanizate (press vulcanization at 150° C. for 30 minutes) and the processability of the unvulcanized rubber composition (using the formulation shown in Table 2) were evaluated. Workability was measured on the workability during roll kneading of the compound on a three-grade scale (○ indicates good wrapping properties, Δ indicates initial wrapping but bagging occurs midway through, × indicates that the product does not wrap around the roll and floats up) each represents something that will happen).

In addition, crack resistance was expressed by converting the number of times until cracking occurred in a bending test into an index.

The crack resistance was measured in accordance with JISK-6301 using a De Matscha bending tester.

The results are shown in Table 4. The physical properties in the index display are expressed with the natural rubber blended vulcanizate (experiment number 13) in Table 4 set as 100.

Table 4 ($1) Same as (Rate 1) in Table 3 (Book 2) Li-5BR, styrene content 14%, 1.2-
Bond amount 72%Tg -28℃, Mooney viscosity
32 (Umbrella 3) Li-SBR, styrene content 15%, 1.
2-Binding amount 34%Tg -63℃, Mooney viscosity 39 (rate 4) Li-5BR, styrene content 24%,
1.2-Binance amount 37%Tg -49℃, Mooney viscosity 35 ($5) Li-BR polybutadiene, 1
．． 2-Amount of bound gold 76%Tg -40°C, Mooney viscosity 35 (Book 6) Polybutadiene, cis 1,4-Amount of bound gold 98%T, -115°C, Mooney viscosity 4
From the results in Table 3 and 4, it can be seen that the rubber composition of the present invention blended with a diene rubber having a Tg of 160''C or less has significantly improved wear resistance and crack resistance.

Example 3 Vulcanized products were obtained by press vulcanization at 150° C. for 30 minutes by changing the blending ratio of Polymer C shown in Table 1 and natural rubber and using the formulation shown in Table 2. The physical properties were measured and the results shown in Table 5 were obtained. Note that the wear resistance and crack resistance are expressed with the results of Experiment No. 21 set as 100.

Table 5

Claims (1)

[Scope of Claims] 1. Styrene-butadiene copolymer rubber (1) obtained by solution polymerization with a styrene content of less than 20% by weight and a trans-1,4 bond in the butadiene moiety of 90% by weight or more.
A rubber composition comprising, as a rubber component, 0 to 40% by weight and 60 to 90% by weight of a diene rubber (2) other than the above having a glass transition temperature of -60°C or lower. 2. The above-mentioned styrene-butadiene copolymer rubber (1) has an active end, an N-substituted aminoketone, an N-substituted thioaminoketone, an N-substituted aminoaldehyde, an N-substituted thioaminoaldehyde, and a molecule It is a reaction product with at least one compound selected from compounds having an atomic group represented by the general formula ▲mathematical formula, chemical formula, table, etc.▼ (in the formula, M represents an oxygen or sulfur atom) The rubber composition according to claim 1.